Introduction: The purpose of this study is the comparison of Eysnck personality dimensions of extraversion, neuroticism and phsychoticism in people with morning-evening cycles.Method: The method of the study is ex post facto. 90 M.A students of Tarbit Modares University were selected by purposeful sampling (30 people with morning cycle and 30 people with evening cycle and 30 balanced people). They completed morning-evening personality questionnaire and also the Eysnck personality questionnaire. Data were analyzed by ANOVA.Results: The results showed that there's no significant difference between the three groups of morning-evening and balanced in relation with extraversion and neuroticism. However, phsychoticism was significantly different in these groups and each group showed higher scores in phychoticism.Discussion and Conclusion: The results show that people with evening cycle has higher psychoticism in comparison with people with morning cycle. This difference is probably due to the wide similarities between eveningness and psychoticism. For example, impulsivity which is a salient feature of psychotic people has a strong relationship with evening cycle. The result can be useful in better planning of optimal usage of people abilities during the day.